Amphibians and reptiles

2. Amphibians
•Amphibians are
animals that can live in
water and have lungs
and legs
•Scientists think that
amphibians evolved
from ancestors of
lungfish-like fishes
•Most of today’s
amphibians are frogs
or salamanders

3. Characteristics of Amphibians
•“Amphibian” means “double life” most
live part of lives on land and part of lives in
water
•Amphibian eggs don’t have a shell to
prevent water loss, so the embryos must
develop in a wet environment
•Are ectotherms body temp. depends on
temp. of environment (cold blooded)

4. •Thin Skin
–Skin is so thin that
amphibians absorb water
instead of drinking it
–Can easily become
dehydrated
–Can breathe with lungs,
but many absorb oxygen
through their skin, which is
full of blood vessels
–May be bright colors; often
to warn predator of poison

5. •Leading a Double Life
–Don’t just get bigger as they
grow, they change form
–After hatching, frog embryo
becomes tadpole and must live
in water
•Gets oxygen through gills and
uses tail to swim
•Later, loses gills and
develops limbs to live on land
–Change from immature form to
adult form is called
metamorphosis

6. Kinds of Amphibians
(1) Caecilians
-look like earthworms or
snakes, but have
amphibian skin
-do not have legs and
have bony scales in
their skin
(2) Salamanders
-do not develop as
tadpoles
-most lose gills and
develop lungs
-a few species keep gills
and live in water for life

7. (3) Frogs and Toads
-90% of amphibians
are frogs or toads
-toads are a type of
frogs (but spend less
time in the water)
(4) Singing Frogs
-sing to communicate
messages that help in
attracting a mate or
marking territories
-most frogs that sing
are males

8. •Amphibians as Ecological
Indicators
–Unhealthy amphibians can be
an early sign of changes in an
ecosystem
–Very sensitive to changes
–Thin skin absorbs any
chemicals in the water or air
–Lungs take in chemicals from
the air
–Climate change also affects
them because they are
ectotherms

9. Reptiles
•Living on Land
–35 million years
after they first
moved on land,
some amphibians
began to change
thick, dry skin, legs
were stronger,
eggs did not dry out
–They had become
reptiles
–Many reptiles are
now extinct most
famous are
dinosaurs

10. •Characteristics of Reptiles
–(1) Thick skin
•Forms a watertight layer that keeps cells from
losing water by evaporation
•Cannot breathe through their skin
•Depend only on lungs for oxygen
(2) Body Temperature
•Nearly all are ectotherms (cold blooded)
•Most live in mild climates
(3) The Amazing Amniotic Egg
•Egg holds fluid that protects the embryo
•Have a shell that keeps it from drying out

12. •Reptile Reproduction
–Usually reproduce
by internal
fertilization
–Reptiles do not go
through
metamorphosis
–Female lays
eggs when they
hatch, the young
look like small
adults

13. •Kinds of Reptiles
–Turtles and Tortoises
•Tortoises live on land,
turtles in the water
•Unique because of their
shells, which is used for
protection
Crocodiles and Alligators
-spend most of their time
in the water
-eyes and nostrils are on
top of their flat heads
-crocodiles have a narrow
head and pointed snout,
and alligator has a broad
head and rounded
snout

14. –Snakes and Lizards
•Most common
reptiles
•Snakes can smell
prey
-Tuataras
-live on only a few
islands off the coast
of New Zealand
-do not have visible
ear openings on
outside of body
-most active when
temp. is low